Benthic oxygen flixes on the Washington shelf and slope

Benthic oxygen fluxes calculated from in situ microelectrode profiles arc compared with benthic flux chamber O2 uptake measurements on a transect of eight stations across the continental shelf and three stations on the slope of Washington State. Station depths ranged from 40 to 630 m and bottom-water oxygen concentrations were 127-38 µM. The fluxes measured by the two methods were similar on the slope, but on the shelf, the chamber flux exceeded the microelectrode flux by as much as a factor of 3-4. We attribute this difference to pore-water irrigation, a process which apparently accounts for the oxidation of a significant amount of organic C in the continental shelf sediments. Combining our diffusive flux data with other data demonstrates clearly that the bottomwater oxygen concentration must play some significant role in determining the sedimentary oxygen consumption rate. Numerical simulation of the microelectrode 0, profiles suggests that roughly half the diffusive 0, flux must be consumed within - 1 mm of the sediment surface. If this conclusion is correct, then the magnitude of the diffusive flux depends both on the bottom-water oxygen concentration and on the supply rate of labile C to the sediment surf'ace.基于原位微电极剖面（in situ microelectrode profiles）计算得到的底栖氧通量（benthic oxygen fluxes），与横跨华盛顿州（Washington State）大陆架的8个站位、陆坡3个站位的断面调查中，采用底栖通量舱室摄氧测量法（benthic flux chamber O2 uptake measurements）获得的结果进行对比。本次研究涉及的站位水深介于40米至630米之间，底层水氧浓度范围为127 μM至38 μM。两种方法测得的通量在陆坡区域结果相近，但在大陆架区域，舱室法测得的通量最高可达微电极法的3~4倍。我们将这一差异归因于孔隙水灌溉（pore-water irrigation）作用——该过程显然主导了大陆架沉积物中大量有机碳（organic C）的氧化反应。将我们的扩散通量数据与其他数据集结合分析后可明确得出：底层水氧浓度在调控沉积耗氧速率（sedimentary oxygen consumption rate）过程中发挥着重要作用。对微电极氧剖面的数值模拟结果显示，约有一半的扩散氧通量会在距沉积物表层约1毫米的范围内被消耗。若该结论成立，则扩散氧通量的大小同时取决于底层水氧浓度与供给至沉积物表层的活性碳（labile C）补给速率。